Add std feature to allow implementing Error trait

Author: tmfink

README.md

@@ -118,9 +118,15 @@ More complex demos welcome!
 
 # Features
 
+- `full`<sup>&dagger;</sup>: do not compile Capstone C library in
+  [diet mode](https://www.capstone-engine.org/diet.html)
+- `std`<sup>&dagger;</sup>: enable `std`-only features, such as the
+  [`Error` trait](https://doc.rust-lang.org/std/error/trait.Error.html)
 - `use_bindgen`: run `bindgen` to generate Rust bindings to Capstone C library
   instead of using pre-generated bindings (not recommended).
 
+<sup>&dagger;</sup>: enabled by default
+
 # Reporting Issues
 
 Please open a [Github issue](https://github.com/capstone-rust/capstone-rs/issues)

capstone-rs/Cargo.toml

@@ -28,7 +28,8 @@ name = "my_benchmark"
 harness = false
 
 [features]
-default = ["full"]
+default = ["full", "std"]
+std = []
 # The 'full' feature, enabled by default, compiles Capstone normally. When disabled,
 # Capstone will be built in Diet mode (https://www.capstone-engine.org/diet.html).
 # This disables some features to reduce the size of the library

capstone-rs/src/error.rs

@@ -72,6 +72,10 @@ capstone_error_def!(
     => UnsupportedX86Masm = CS_ERR_X86_MASM;
 );
 
+// Required until https://github.com/rust-lang/rust/issues/103765 is resolved
+#[cfg(feature = "std")]
+impl std::error::Error for Error {}
+
 pub type CsResult<T> = result::Result<T, Error>;
 
 impl fmt::Display for Error {

capstone-rs/src/lib.rs

@@ -1,16 +1,16 @@
 #![doc = include_str!("../../README.md")]
-#![no_std]
+#![cfg_attr(not(feature = "std"), no_std)]
 
 // The `vec` macro cannot be imported directly since it conflicts with the `vec` module
 #[allow(unused_imports)]
 #[macro_use]
 extern crate alloc;
 
-#[cfg(test)]
+#[cfg(any(test, not(feature = "std")))]
 #[macro_use]
 extern crate std;
 
-#[cfg(test)]
+#[cfg(any(test, not(feature = "std")))]
 #[global_allocator]
 static ALLOCATOR: std::alloc::System = std::alloc::System;